Review and extension of compliance information for common crack growth specimens

Elastic compliance expressions for compact type (CT) and WOL specimens have been formulated for a wide range of crack lengths (0.2 a/W 0.975) using results from Newman's modified boundary collection techniques and Wilson's deep crack analysis. The location of the axis of rotation of the specimen arms at various crack lengths has been calculated and subsequently used in a proposed extrapolation technique to predict compliance at any location of the specimen convenient for measuring deflection during a crack growth test. The predicted compliances were found to be in excellent agreement with expreimental values for the two specimen types considered. Compliance expressions are also included for the center crack tension specimen.

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Résumé Des expressions de compliance élastique pour des éprouvettes du type compacte (CT) et WOL ont été formulées pour une gamme large de longueurs de fissuration (a/W compris entre 0.2 et 0.975) en utilisant les résultats tirés de l'application des techniques modifiées de collationnement aux frontières selon Newman ainsi que de l'analyse d'une fissure profonde d'après Wilson. La localisation de l'axe de rotation des bras de l'éprouvette pour différents longueurs de fissure a été calculée et utilisée en conséquence dans une technique d'extrapolation proposée pour prédire la compliance à toutes localisations de l'éprouvette convenant pour la mesure de la déflection durant un essai de croissance de fissure. Les compliances prédites ont été trouvées en excellent accord avec les valeurs expérimentales pour les deux types d'éprouvette considérés. Les expressions de compliance ont également été formulées pour un éprouvette de traction à fissure centrale.

     

Personality constellations in incarcerated psychopathic men.

Advances in the operationalization of psychopathy have led to an increased understanding of the boundaries, structure, and nomological network of this construct, although significant questions remain. The empirical identification of replicable and theoretically meaningful psychopathy subtypes may help to improve the classification and diagnosis of this condition. We conducted a classification study of 91 incarcerated men who met conventional criteria for high levels of psychopathy using the Psychopathy Checklist-Revised. We expanded on the methodology of previous research on psychopathy subtypes by utilizing a comprehensive personality assessment instrument and a prototype matching approach to classification. The analyses revealed a primary (narcissistic) subtype and a secondary (hostile and dysregulated) subtype that were broadly consistent with the previous literature. External validation analyses, statistical controls, and incremental validity analyses provided substantial support for the primary and secondary subtypes. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Second Generation Micro-Orifice Uniform Deposit Impactor, 120 MOUDI-II: Design,Evaluation, and Application to Long-Term Ambient Sampling

The original MOUDI (Micro-Orifice Uniform Deposit Impactor) cascade impactor, reported in the literature in 1991, used an external gear system to achieve a uniform deposit and was intended for industrial hygiene studies with sample times in the range of minutes to a few hours. To facilitate much longer run times, a second generation MOUDI, MOUDI-II, which uses internal electric motors to rotate the impaction plates, was developed. Three model 120 MOUDI-IIs were used in a 32-month program to sample ambient atmospheric aerosols at several industrial and urban locations in Minnesota. For these sampling locations, each 120 MOUDI-II operated continuously for a minimum of five, and optimally 7 days, to collect a sample at a site. During these community sampling events, the three 120 MOUDI-IIs logged 4007, 2637, and 3230 h of operating time, respectively. A laboratory side-by-side comparison of the three 120 MOUDI-IIs showed good agreement amongst the three 120 MOUDI-IIs and, thus, the particle size distributions were independent of the 120 MOUDI-II used. Application of the 120 MOUDI-IIs for long-term ambient sampling was demonstrated by comparing size distributions from the background locations: Minneapolis, Duluth and Ely, Minnesota, representing urban, light industrial, and pristine area type of aerosols, respectively. PM_2.5 averages from Minneapolis and Duluth compare well with three-year averages from state regulatory sampling.

Copyright 2014 American Association for Aerosol Research     

On estimating percentiles of the Weibull distribution by the linear regression method

Probability estimators developed previously by the authors have been used to obtain unbiased estimates of the Weibull parameters by the linear regression method. Using these unbiased estimators, percentiles of the Weibull distribution have been estimated. Since these percentiles are determined from the estimated parameters, they also have distributions and subsequently are determined for five sample sizes. Analysis has shown that the distributions of these estimated percentiles are neither normal, lognormal, three-parameter Weibull nor three-parameter log-Weibull. A new methodology to estimate the percentile with a specified level of confidence has been introduced. The step-by-step use of the methodology is demonstrated by examples in this paper.     

Modelling and measurement of crack closure and crack growth following overloads and underloads

Ignoring crack growth retardation following overloads can result in overly conservative life predictions in structures subjected to variable amplitude fatigue loading. Crack closure is believed to contribute to the crack growth retardation, although the specific closure mechanism is debatable. The delay period and corresponding crack growth rate transients following overload and overload/underload cycles were systematically measured as a function of load ratio (R) and overload magnitude. These responses are correlated in terms of the local “driving force” for crack growth, i.e. the effective stress intensity factor range (ΔK_eff). Experimental results are compared with the predictions of a Dugdale-type crack closure model and improvements in the model are suggested.     

Evaluation and comparison of fault-tolerant software techniques

Four implementations of fault-tolerant software techniques are evaluated with respect to hardware and design faults. Project participants were divided into four groups, each of which developed fault-tolerant software based on a common specification. Each group applied one of the following techniques: N-version programming, recovery block, concurrent error-detection, and algorithm-based fault tolerance. Independent testing and modeling groups analyzed the software. The testing group subjected it to simulated design and hardware faults. The data were then mapped into a discrete-time Markov model developed by the modeling group. The effectiveness of each technique with respect to availability, correctness, and time to failure given an error, as shown by the model, is contrasted with measured data. The model is analyzed with respect to additional figures of merit identified during the modeling process, and the techniques are ranked using an application taxonomy     

On the determination of the interval hull of linear interval equations

We present new methods for solving special classes of linear interval equations by means of suitable selection systems. First we prove some theorems characterizing the extremal points of the solution set. For invers-stable interval matrices and systems whose solution set are contained in one orthant we give algorithms to select such systems the solutions of which generate the interval hull.